Cystic fibrosis, the most common lethal autosomal recessive inherited disease, is linked to non-functional chloride channel CFTR (for Cystic Fibrosis Trans-membrane Conductance Regulator).
Deletion of phenylalanine 508 (Δ508F CFTR) in the CFTR protein encoding gene accounts for the most prevalent mutation in cystic fibrosis patients and represents almost 70% of the mutations. Δ508F CFTR protein is unable to translocate to the plasma membrane where CFTR normally displays its physiological activity. Other mutations of human CFTR which may be cited are G542X, G551D, N1303K, W1282X, R553X, 621+1G, 1717-1G, R117H and R1162X. Over the 1900 different mutations that have been described, only four of these, besides Δ508F, represent more than 1% of cases.
In addition to the well-established role of CFTR in the function of pulmonary epithelial cells, the importance of CFTR in microbicide activity of pulmonary macrophages has been shown, as well as CFTR also augmenting the neutrophil microbicide capacity.
Therefore, one strategy aimed at developing novel molecules targeting the root cause of CF rather than disease symptoms, lies on the improvement of mutant CFTR functions.
Despite a tremendous effort in particular within said strategy made over the last two decades to understand pathogenesis of cystic fibrosis, there is no cure for the disease.
(R)-roscovitine is a potent cyclin-dependent kinase inhibitor that was initially proposed to be used for treating various cancers (see WO 97/20842).
(R)-roscovitine, (2-(R)-(1-ethyl-2-hydroxyethylamino)-6-benzylamino-9-isopropylpurine), which is a substituted derivative of purine, and closely related derivatives thereof, were shown to rescue some Δ508F CFTR plasma membrane translocation (see WO 2006/042949).
Nevertheless, it is still not clear why the cells of innate immune system including macrophages and neutrophils are unable to eradicate microbial infection. In the cystic fibrosis lung, microbial colonization, predominantly with Pseudomonas aeruginosa, and massive lung tissue damage by recruited neutrophils lead to severe bronchial damage, respiratory insufficiency, and death. Defects in innate immune system could have important consequences for microbial defence in cystic fibrosis patients.
Current treatment of cystic fibrosis relies upon treating microbial infections that are consequently appearing at one stage of this disease. Antimicrobials and more particularly antibiotics are largely used, with numerous drawbacks because of increasingly highly resistant microorganisms to the known antibiotics.
In order to develop an alternative strategy, the inventors investigated another pathway, in connection to alveolar macrophages (AMs), and identified compounds which could resolve microbial infection without the use of antimicrobials.
In order to perform their major function, macrophages must ingest and destroy microbial pathogens. Following engulfment of pathogens by phagocytosis, the phagosomes fuse with lysosomes into phago-lysosomes where pathogens are digested by various proteolytic and lipolytic enzymes. Optimal functioning of the lysosomal degrading enzymes requires an acidic pH, which characterizes the lysosomes lumen. Generation of low phago-lysosomes pH is primarily driven by the V-ATPases, proton pumps that use cytoplasmic ATP to load H+ into the organelle derived during lysosomes fusion to the maturing phagosomes.
It was recently shown that murine alveolar macrophages employ CFTR as a major charge shunt mechanism thereby allowing acidification of phago-lysosomal compartment and consequent bacterial killing (Deriy et al., 2009; Di et al., 2006).
Indeed it was shown that the intra-phago-lysosomal pH of alveolar macrophages of individuals having cystic fibrosis is less acidic (pH 7.2), as compared with those of healthy individuals (pH 5.2). It was further shown that there is a tight correlation between CFTR genotype and levels of lysosomal acidification and microbial killing.
Accordingly, there is a need for providing a method of treatment of cystic fibrosis condition in an individual in need thereof.
There is furthermore a need for providing a treatment for alleviating symptoms associated with cystic fibrosis condition in an individual in need thereof.
There is a need to provide a treatment of microbial infection that is most frequently associated with cystic fibrosis condition in an individual in need thereof.
There is a need to provide a treatment of microbial infection that is most frequently associated with cystic fibrosis condition, by limiting the use of antibiotics in an individual in need thereof.
There is also a need for providing a treatment for alleviating symptoms associated with cystic fibrosis condition in an individual in need thereof, said treatment being independent from the mutation of the CFTR encoding gene.
There is still a need to provide molecules rescuing the microbicide function in CF pulmonary alveolar macrophages (AMs).
M3 is a known metabolite of (R)-Roscovitine, which does not exhibit kinase inhibiting properties. It was in particular described in patent application WO 2004/016612.